Display device with prism layer

ABSTRACT

It is an object to propose a display device in which reflection of external light on a reflective polarizing plate is prevented and also extraction efficiency of light from a light-emitting layer is improved. If the display device has a light-emitting layer provided over a reflective electrode, a transparent electrode provided over the light-emitting layer, a transparent substrate provided over the transparent electrode, a reflective polarizing plate provided over the transparent substrate, a quarter wave plate provided over the reflective polarizing plate, and a polarizing plate provided over the quarter wave plate, reflection of an outside image can be suppressed, and light emitted in the light-emitting layer can be extracted efficiently.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a display device in which an elementhaving a structure including an anode, a cathode, and a thin film whichemits light by electroluminescence (hereinafter, referred to as “EL”)interposed between the anode and the cathode is provided over asubstrate.

2. Description of the Related Art

An EL element is an element which obtains light emission by forming athin film containing an organic compound or an inorganic compound, or acrystal between a cathode and an anode and feeding current between thecathode and the anode. In recent years, especially an EL element inwhich a thin film containing an organic compound as its main constituent(hereinafter, referred to as a light-emitting layer) is placed between acathode and an anode, i.e., an organic EL element, has been activelydeveloped.

An organic EL element is expected to be applied in various fields, andis considered to be applied not only to a lighting apparatus but also toa display or the like used for a mobile phone or a personal computer.The organic EL element is manufactured by interposing a material whichemits light by feeding current between a pair of electrodes. The organicEL element emits light by itself, and thus does not need a light sourcesuch as a backlight, differently from a liquid crystal. Also, theelement itself is extremely thin. Therefore, the organic EL element hasa great advantage in manufacturing a thin and lightweight display.

For example, as such a display, a display device is proposed, in whichan organic EL element using metal having high reflexivity for a cathodeand a transparent electrode for an anode is provided over a substrate.By using the metal having high reflexivity for the cathode, emissionluminance from a light-emitting layer can be enhanced; however, on theother hand, there is a problem that an outside image is reflected whenexternal light is reflected on the metal surface, which causesdeterioration of image display characteristics, for example a viewer hasdifficulty in seeing a display image and brightness of the display imagegets dark. In order to solve the problem, there is a proposed method ofsuppressing reflection of an outside image (or outside light) byproviding antireflection means. For example, a display device (PatentDocument 1: Japanese Published Patent Application No. 2005-100789)provided with antireflection means including a quarter wave plate, areflective polarizing plate, and an absorptive polarizing plate, or adisplay device (Patent Document 2: Japanese Published Patent ApplicationNo. H11-45058) provided with antireflection means including a wavelengthcorrecting plate, a plane linear polarization beam splitter, and apolarizing plate is disclosed.

However, in the display device provided with antireflection meansincluding a quarter wave plate, a reflective polarizing plate, and anabsorptive polarizing plate, or the display device provided withantireflection means including a wavelength correcting plate, a planelinear polarization beam splitter, and a polarizing plate, there arepossibilities not only that reflection of an outside image when externallight is reflected on a cathode surface cannot be suppressed, but alsothat part of external light which enters the display device does notpass through the reflective polarizing plate or the plane linearpolarization beam splitter and is reflected on the surface, andaccordingly, the reflection of the outside image cannot be eliminatedcompletely.

SUMMARY OF THE INVENTION

It is an object of the present invention to propose a display device inwhich reflection of external light on a reflective polarizing plate isprevented and also extraction efficiency of light from a light-emittinglayer is enhanced.

One feature of the present invention is a display device having alight-emitting layer provided over a reflective electrode, a transparentelectrode provided over the light-emitting layer, a reflectivepolarizing plate provided over the transparent electrode, a quarter waveplate provided over the reflective polarizing plate, and a polarizingplate provided over the quarter wave plate.

Another feature of the present invention is a display device having atransparent electrode, a light-emitting layer, and a reflectiveelectrode over one surface of a substrate, and a reflective polarizingplate, a quarter wave plate, and a polarizing plate over the othersurface of the substrate, where the quarter wave plate is providedbetween the reflective polarizing plate and the polarizing plate.

Another feature of the present invention is a display device having atransparent electrode, a light-emitting layer, and a reflectiveelectrode over one surface of a transparent substrate, and a reflectivepolarizing plate, a broadband quarter wave plate having an effect as aquarter wave plate in a range of visible light, and a polarizing plateover the other surface of the transparent substrate, where the broadbandquarter wave plate is provided between the reflective polarizing plateand the polarizing plate.

Another feature of the present invention is a display device having alight-emitting layer provided over a reflective electrode, a transparentelectrode provided over the light-emitting layer, a substrate providedover the transparent electrode, a reflective polarizing plate providedover the substrate, a quarter wave plate provided over the reflectivepolarizing plate, and a polarizing plate provided over the quarter waveplate.

Another feature of the present invention is a display device having areflective electrode provided over a substrate, a light-emitting layerprovided over the reflective electrode, a transparent electrode providedover the light-emitting layer, a reflective polarizing plate providedover the transparent electrode, a quarter wave plate provided over thereflective polarizing plate, and a polarizing plate provided over thequarter wave plate.

Another feature of the present invention is a display device having afirst quarter wave plate provided over a first polarizing plate, a firstreflective polarizing plate provided over the first quarter wave plate,a substrate provided over the reflective polarizing plate, a firsttransparent electrode provided over the substrate, a light-emittinglayer provided over the first transparent electrode, a secondtransparent electrode provided over the light-emitting layer, a secondreflective polarizing plate provided over the second transparentelectrode, a second quarter wave plate provided over the secondreflective polarizing plate, and a second polarizing plate provided overthe second quarter wave plate.

Another feature of the present invention is a display device having aquarter wave plate provided over a polarizing plate, a reflectivepolarizing plate provided over the quarter wave plate, a substrateprovided over the reflective polarizing plate, a thin film transistorhaving a semiconductor film including a source region or a drain region,which is provided over the substrate, an interlayer insulating filmhaving a contact hole reaching the source region or the drain region,which is provided over the thin film transistor, a wiring electricallyconnected to the source region or the drain region, which is providedover the interlayer insulating film, a transparent electrode providedover the interlayer insulating film and the wiring, a light-emittinglayer provided over the transparent electrode, and a reflectiveelectrode provided over the light-emitting layer.

Another feature of the present invention is a display device having athin film transistor having a semiconductor film including a sourceregion or a drain region, which is provided over a substrate, aninterlayer insulating film having a contact hole reaching the sourceregion or the drain region, which is provided over the thin filmtransistor, a wiring electrically connected to the source region or thedrain region, which is provided over the interlayer insulating film, areflective electrode provided over the interlayer insulating film andthe wiring, a light-emitting layer provided over the reflectiveelectrode, a transparent electrode provided over the light-emittinglayer, a reflective polarizing plate provided over the transparentelectrode, a quarter wave plate provided over the reflective polarizingplate, and a polarizing plate provided over the quarter wave plate.

Another feature of the present invention is a display device having afirst quarter wave plate provided over a first polarizing plate, a firstreflective polarizing plate provided over the first quarter wave plate,a substrate provided over the first reflective polarizing plate, a thinfilm transistor having a semiconductor film including a source region ora drain region, which is provided over the substrate, an interlayerinsulating film having a contact hole reaching the source region or thedrain region, which is provided over the thin film transistor, a wiringelectrically connected to the source region or the drain region, whichis provided over the interlayer insulating film, a first transparentelectrode provided over the interlayer insulating film and the wiring, alight-emitting layer provided over the first transparent electrode, asecond transparent electrode provided over the light-emitting layer, asecond reflective polarizing plate provided over the second transparentelectrode, a second quarter wave plate provided over the secondreflective polarizing plate, and a second polarizing plate provided overthe second quarter wave plate.

Another feature of the present invention is a display device in which aprism is formed between the substrate and the reflective polarizingplate.

Another feature of the present invention is a display device having atransparent electrode, a light-emitting layer, and a reflectiveelectrode over one surface of a substrate, and a first quarter waveplate, a reflective polarizing plate, a second quarter wave plate, and apolarizing plate over the other surface of the substrate.

Another feature of the present invention is a display device having alight-emitting layer provided over a reflective electrode, a transparentelectrode provided over the light-emitting layer, a substrate providedover the transparent electrode, a first quarter wave plate provided overthe substrate, a reflective polarizing plate provided over the firstquarter wave plate, a second quarter wave plate provided over thereflective polarizing plate, and a polarizing plate provided over thesecond quarter wave plate.

Another feature of the present invention is a display device having asecond quarter wave plate provided over a polarizing plate, a reflectivepolarizing plate provided over the second quarter wave plate, a firstquarter wave plate provided over the reflective polarizing plate, asubstrate provided over the first quarter wave plate, a thin filmtransistor having a semiconductor film including a source region or adrain region, which is provided over the substrate, an interlayerinsulating film having a contact hole reaching the source region or thedrain region, which is provided over the thin film transistor, a wiringelectrically connected to the source region or the drain region, whichis provided over the interlayer insulating film, a transparent electrodeprovided over the interlayer insulating film and the wiring, alight-emitting layer provided over the transparent electrode, and areflective electrode provided over the light-emitting layer.

Another feature of the present invention is a display device in which aprism is formed between the substrate and the first quarter wave plate.

Another feature of the present invention is a display device in whichthe quarter wave plate, the first quarter wave plate, or the secondquarter wave plate is a broadband quarter wave plate.

Another feature of the present invention is an electronic apparatushaving the display device.

In the present invention, reflection of an outside image when externallight is reflected on a reflective polarizing plate can be suppressed,and display characteristics of an image can be improved. In addition,light emitted in a light-emitting layer can be extracted efficiently,and decrease in brightness of a display image can be suppressed.

BRIEF DESCRIPTION OF DRAWINGS

In the accompanying drawings:

FIGS. 1A and 1B are schematic cross-sectional views each showing adisplay device;

FIGS. 2A and 2B are schematic cross-sectional views each showing adisplay device;

FIG. 3 is a schematic cross-sectional view showing a display device;

FIGS. 4A and 4B are schematic cross-sectional views each showing adisplay device;

FIGS. 5A to 5E are views each showing an example of a manufacturingprocess of a display device;

FIGS. 6A to 6D are views each showing an example of a manufacturingprocess of a display device;

FIG. 7 is a view showing an example of a manufacturing process of adisplay device;

FIG. 8 is a view showing a structure of a light-emitting layer includedin a display device;

FIGS. 9A and 9B are views each showing a panel of a display device;

FIGS. 10A and 10B are views each showing a panel of a display device;and

FIGS. 11A to 11E are views each showing an electronic apparatus using adisplay device.

DETAILED DESCRIPTION OF THE INVENTION

A best mode for carrying out the present invention will be explainedwith reference to drawings. However, the present invention is notlimited to the modes below, and it is easily understood by those skilledin the art that the modes and details can be modified in various wayswithout departing from the purpose and the scope of the presentinvention. Therefore, the present invention is not interpreted as beinglimited to the description of the embodiment modes to be given below. Itis to be noted that, in the structure hereinafter explained, thereference numerals denoting the same portions are used in common indifferent drawings and the repeated explanation is omitted. In addition,following Embodiment Modes 1 to 7 can be freely combined with each otherto be used.

It is to be noted that, in the present specification, an axis ofpolarizing axes of a polarizing plate or a reflective polarizing plate,which transmits light, is referred to as a transmission axis. Also, anaxis of the polarizing axes of the polarizing plate, which absorbslight, is referred to as an absorption axis. It is to be noted that thetransmission axis and the absorption axis cross at right angles. Such anabsorptive polarizing plate having an absorption axis is simply referredto as a polarizing plate. In addition, a polarizing plate having afunction of transmitting light of a particular polarization componentand reflecting light of other polarization component is referred to as areflective polarizing plate.

Here, a linear polarization reflective polarizing plate or a circularpolarization reflective polarizing plate can be used as the reflectivepolarizing plate. In the present specification, the linear polarizationreflective polarizing plate indicates a plate which has properties oftransmitting one polarization component of linear polarization andreflecting other polarization component (that is, properties oftransmitting and reflecting any of components of the linear polarizationsuch as a P wave and an S wave, for example transmitting the P wavecomponent and reflecting the S wave component). The circularpolarization reflective polarizing plate indicates a plate which hasproperties of transmitting a component with one rotation direction amongright-hand circular polarization and left-hand circular polarization andreflecting the other component. As the linear polarization reflectivepolarizing plate, a multilayer film in which transparent layers eachhaving different refractive index are stacked, or the like can be used,for example. Also, as the circular polarization reflective polarizingplate, a substance having a cholesteric layer, or the like can be used,for example.

In addition, in the present specification, a combination of a half waveplate and a quarter wave plate may also be used instead of a quarterwave plate. Moreover, in the present specification, a broadband quarterwave plate having an effect as a quarter wave plate in a range ofvisible light (preferably, 380 to 780 nm) is also referred to as aquarter wave plate.

Embodiment Mode 1

In this embodiment mode, a display device having a reflective polarizingplate, a quarter wave plate, and a polarizing plate will be explained.In FIGS. 1A and 1B, part of the display device of this embodiment modeis shown. It is to be noted that this structure is effective fordisplays such as PDP, SED, and FED as well as an organic EL display oran inorganic EL display.

In the display device of this embodiment mode, as shown in FIGS. 1A and1B, a transparent electrode 11, a light-emitting layer 12, and areflective electrode 13 are stacked over a substrate 100, and areflective polarizing plate 14, a quarter wave plate 15, and apolarizing plate 16 are stacked over a surface of the substrate 100,which is opposite to the surface provided with the transparent electrode11. In other words, the display device has a structure in which thereflective electrode 13, the light-emitting layer 12, the transparentelectrode 11, the substrate 100, the reflective polarizing plate 14, thequarter wave plate 15, and the polarizing plate 16 are sequentiallystacked. In this embodiment mode, a structure in which light emissionfrom the light-emitting layer 12 is extracted from the transparentelectrode 11 side (the substrate 100 side) is employed, and lightemission can be obtained by feeding current between the transparentelectrode 11 and the reflective electrode 13.

The polarizing plate 16 has functions of transmitting a linearpolarization component having a vibrating surface which is parallel toits transmission axis and absorbing a linear polarization componenthaving a vibrating surface which crosses the transmission axis at rightangles.

In this embodiment mode, in a case of using a linear polarizationreflective polarizing plate as the reflective polarizing plate, atransmission axis of the reflective polarizing plate 14 and a slow axisof the quarter wave plate 15 are arranged so as to have an angle of 45°or 135° between them. Also, in a case of using the linear reflectivepolarizing plate, the transmission axis of the reflective polarizingplate 14 and a transmission axis of the polarizing plate 16 are arrangedso as to be parallel to each other.

In this embodiment mode, since a structure in which light emission fromthe light-emitting layer 12 is extracted through the substrate 100 isemployed, the substrate 100 needs to be a transparent substrate. As thesubstrate 100, a glass substrate, a quartz substrate, a flexiblesubstrate, or the like can be used, for example. The flexible substratemeans a substrate which can be bent, and a plastic substrate or the likewhich is formed of polyimide, acrylic, polyethylene terephthalate,polycarbonate, polyarylate, or polyether sulfone, or the like can begiven, for example. In addition, a thin film-formed substrate formed ofpolypropylene, polyester, vinyl, polyvinyl fluoride, vinyl chloride, orthe like can also be used. A planarizing film may be applied to thesesubstrates as needed, or a nitride film, an oxide film, or a stackedfilm of these films may be formed. Alternatively, these substrates maybe used after being polished by CMP or the like.

As the transparent electrode 11, indium tin oxide (ITO), indium tinoxide containing silicon oxide (ITSO), zinc oxide (ZnO), indium zincoxide (IZO) which is formed using a target in which 2 to 20 wt % of zincoxide (ZnO) is further mixed with indium oxide containing silicon oxide,zinc oxide containing gallium (GZO), tin oxide (SnO₂), indium oxide(In₂O₃), or the like can be used.

The light-emitting layer 12 contains a light-emitting substance. Forexample, the light-emitting layer 12 has a structure in which a holetransporting layer, a light-emitting layer, and an electron transportinglayer are sequentially stacked over the transparent electrode 11. Thestructure of the light-emitting layer 12 is not limited thereto, and itis acceptable as long as the structure has at least a light-emittinglayer. Besides the light-emitting layer, for example, functional layerssuch as an electron injecting layer, an electron transporting layer, ahole blocking layer, a hole transporting layer, and a hole injectinglayer may be freely combined with each other. It is to be noted thatsince the transparent electrode 11 serves as an anode in this embodimentmode, the hole injecting layer, the hole transporting layer, the holeblocking layer, the light-emitting layer, the electron transportinglayer, and the electron injecting layer are sequentially stacked fromthe transparent electrode 11 side. In addition, a mixed layer or a mixedjunction of the above layers may also be formed. It is to be noted thata boundary between layers is not necessarily clear, and there is a casewhere materials forming adjacent layers are partially mixed and theboundary between the layers is unclear. An organic material and aninorganic material can be used for each layer. As the organic material,any of materials of high molecular, middle molecular, and low molecularcan be used. Further, the middle molecular material corresponds to a lowpolymer in which the number of repeated structural units (the degree ofpolymerization) is approximately 2 to 20.

As the reflective electrode 13, highly reflective metal (e.g., metalhaving reflectivity of 40% or more) is preferably used. For example,aluminum (Al), silver (Ag), an AlLi alloy and a MgAg alloy which arealloys containing the metal, and the like can be used. In addition, thereflective electrode 13 may have a stacked structure of highlyreflective metal and other electrode material. An electron injectingproperty can be enhanced by forming a thin film of alkali metal oralkali earth metal (e.g., approximately 5 nm), and stacking the film andhighly reflective metal.

Here, a case where the reflective polarizing plate 14 is a linearpolarization reflective polarizing plate is explained. First, an opticalcomponent (referred to as first polarization) of external light whichenters from an observation surface of a display device, i.e., an upperside of the polarizing plate 16, which is parallel to an absorption axisof the polarizing plate 16, is absorbed in the polarizing plate 16, andsecond polarization which is parallel to a transmission axis of thepolarizing plate 16 enters the display device. The second polarizationis converted to right-hand or left-hand circular polarization by passingthrough the quarter wave plate 15. In this embodiment mode, a case wherethe second polarization is converted to the right-hand circularpolarization is considered. A polarization component of the secondpolarization converted to right-hand circular polarization, which doesnot coincide with a transmission axis of the reflective polarizing plate14, is reflected on the reflective polarizing plate 14 and returns tothe quarter wave plate 15 as left-hand circular polarization. Theleft-hand circular polarization is converted to third polarizationhaving a polarizing axis which is perpendicular to a polarizing axis ofthe second polarization by passing through the quarter wave plate 15. Inother words, the third polarization has a polarizing axis which isparallel to the absorption axis of the polarizing plate 16. Similarly,in a case of the left-hand circular polarization, third polarizationhaving a polarizing axis which is parallel to the absorption axis of thepolarizing plate 16 is emitted. Therefore, the third polarization isabsorbed without passing through the polarizing plate 16.

In addition, a polarization component of the second polarization, whichcoincides with a transmission axis of the reflective polarizing plate14, passes through the reflective polarizing plate 14. Then, thepolarization component is reflected on the reflective electrode 13 andpasses through the reflective polarizing plate 14 again, and thereafter,is converted to fourth polarization having a polarization componentwhich is perpendicular to the polarizing axis of the second polarizationby passing through the quarter wave plate 15. Since the fourthpolarization coincides with the absorption axis of the polarizing plate16, the fourth polarization is absorbed without passing through thepolarizing plate 16. Therefore, a component of external light whichenters the display device is absorbed in the polarizing plate 16, andthe external light is not emitted outside again; therefore, reflectionof an outside image can be suppressed.

On the other hand, a polarization component of light emitted in thelight-emitting layer 12, which is parallel to the transmission axis ofthe reflective polarizing plate 14 passes through the reflectivepolarizing plate 14, becomes circular polarization through the quarterwave plate 15, and light having the same component as that of thetransmission axis passes through the polarizing plate 16 to be emittedoutside the display device. The other polarization component isreflected on the reflective polarizing plate 14 to return in a directionof the light-emitting layer 12, and is reflected on the reflectiveelectrode 13 to enter the reflective polarizing plate 14 again. Here,light having a polarizing axis which is not parallel to the polarizingaxis of the reflective polarizing plate 14 is repeatedly reflectedbetween the reflective polarizing plate 14 and the reflective electrode13. By being repeatedly reflected, the polarizing axis is displaced, thepolarizing axis of the repeatedly reflected light becomes parallel tothe polarizing axis of the reflective polarizing plate 14, and the lightis emitted from the display device by passing through the reflectivepolarizing plate 14, the quarter wave plate 15, and the polarizing plate16. Therefore, a light emission component which has not conventionallybeen able to be used can be utilized effectively, and enhancement ofbrightness of a display image can be attempted.

A polarizing plate 17 may be additionally provided between thereflective polarizing plate 14 and the quarter wave plate 15 (FIG. 1B).In that case, the polarizing plate 17 is arranged so that a transmissionaxis of the polarizing plate 17 coincides with that of the polarizingplate 16. By providing the polarizing plate 17, polarization of thesecond polarization converted in the right-hand circular polarization,which does not coincide with the transmission axis of the reflectivepolarizing plate 14 and is reflected on the reflective polarizing plate14, is absorbed in the polarizing plate 17; therefore, external light isnot emitted outside again. Thus, reflection of an outside image can besuppressed more effectively.

In addition, a case where the reflective polarizing plate 14 is acircular polarization reflective polarizing plate is explained. First,an optical component (referred to as first polarization) of externallight which enters from an observation surface of the display device,i.e., an upper side of the polarizing plate 16, which is parallel to anabsorption axis of the polarizing plate 16, is absorbed in thepolarizing plate 16, and second polarization which is parallel to atransmission axis of the polarizing plate 16 enters the display device.The second polarization is converted to right-hand or left-hand circularpolarization by passing through the quarter wave plate 15. In thisembodiment mode, a case where the second polarization is converted tothe right-hand circular polarization is considered. Here, the reflectivepolarizing plate 14 has functions of transmitting a left-hand circularpolarization component and reflecting a right-hand circular polarizationcomponent. The second polarization converted to right-hand circularpolarization is reflected on the reflective polarizing plate 14, returnsto the quarter wave plate 15, and passes through the quarter wave plate15; accordingly, the second polarization is converted to thirdpolarization having a polarizing axis which is perpendicular to thepolarizing axis of the second polarization. In other words, the thirdpolarization has a polarizing axis which is parallel to the absorptionaxis of the polarizing plate 16. Here, in a case where the secondpolarization is converted to left-hand circular polarization at thequarter wave plate 15, the reflective polarizing plate 14 havingfunctions of transmitting right-hand circular polarization andreflecting left-hand circular polarization is used so that the secondpolarization is converted to the third polarization having a polarizingaxis which is parallel to the absorption axis of the polarizing plate16. Therefore, a component of external light which enters the displaydevice is absorbed in the polarizing plate 16, and the external light isnot emitted outside again. Thus, reflection of an outside image can besuppressed.

On the other hand, a circular polarization component of light emitted inthe light-emitting layer 12 which does not coincide with a spiralrotation direction of a cholesteric layer of the reflective polarizingplate passes through the reflective polarizing plate 14, the quarterwave plate 15, and the polarizing plate 16, and emitted from the displaydevice. In addition, a circular polarization component which coincideswith the spiral rotation direction is reflected on the reflectivepolarizing plate 14 to return in a direction of the light-emitting layer12, and is reflected on the reflective electrode 13 to enter thereflective polarizing plate 14 again. Here, polarization which does notpass through the reflective polarizing plate 14 is repeatedly reflectedbetween the reflective polarizing plate 14 and the reflective electrode13. By the repetition reflection, the polarizing axis is displaced,repeatedly reflected light passes through the reflective polarizingplate 14, the quarter wave plate 15, and the polarizing plate 16, and isemitted from the display device. Therefore, a light emission componentwhich has not conventionally been able be to be used can be utilizedeffectively, and enhancement of brightness of a display image can beattempted.

In this embodiment mode, an antireflection film, a non-antireflectionfilm, or the like may be provided. The antireflection film suppressesreflection of external light on a surface by stacking thin films eachhaving different refractive index, or the like. By providing theantireflection film, the reflection of external light on the surface ofthe polarizing plate 16 can be suppressed, and further, reflection of anoutside image can be suppressed.

Also, by using a broadband quarter wave plate which has a function as aquarter wave plate in a range of visible light (preferably, 380 to 780nm) as the quarter wave plate, a favorable quarter wave characteristicin the visible light range can be obtained, and in addition, not onlyexternal light can be made to disappear in a wide range but also lightemitted from the light-emitting layer 12 can be extracted efficiently.

In the display device of this embodiment mode, the reflection of anoutside imager when external light is reflected on the reflectivepolarizing plate 14 can be suppressed, and display characteristics of animage can be improved. In addition, light emitted in the light-emittinglayer 12 can be extracted efficiently, and improvement in brightness ofa display image can be attempted.

Embodiment Mode 2

In this embodiment mode, a case where a prism layer is provided betweena reflective polarizing plate 14 and a substrate 100 will be explained.It is to be noted that, in FIGS. 2A and 2B, the same portions as thosein FIGS. 1A and 1B are denoted by the same reference numerals, and theexplanation is omitted. In FIGS. 2A and 2B, part of a display device ofthis embodiment mode is shown.

In the display device of this embodiment mode, as shown in FIG. 2A, atransparent electrode 11, a light-emitting layer 12, and a reflectiveelectrode 13 are stacked over a substrate 100, and a prism layer 201, areflective polarizing plate 14, a quarter wave plate 15, and apolarizing plate 16 are sequentially stacked over a surface of thesubstrate 100, which is opposite to the surface provided with thetransparent electrode 11. In other words, the display device has astructure in which the reflective electrode 13, the light-emitting layer12, the transparent electrode 11, the substrate 100, the prism layer201, the reflective polarizing plate 14, the quarter wave plate 15, andthe polarizing plate 16 are sequentially stacked.

In this embodiment mode, the prism layer 201 is a comb-shaped filmmaterial provided in order to displace a polarizing axis ofpolarization, in which projections are formed in stripe and a crosssection in a direction perpendicular to the stripe on the surface is arandom size. It is to be noted that, in this embodiment mode, the prismlayer 201 is not particularly limited as long as the prism layer is ascattering layer which can displace the polarizing axis of thepolarization. As such a scattering layer, a thin film 203 in which asubstance (or a particle) 202 formed of materials each having adifferent size or refractive index are dispersed may be used, forexample (FIG. 2B). In addition, both the scattering layer and the prismlayer may also be provided.

In this embodiment mode, in a case of using a linear polarizationreflective polarizing plate as the reflective polarizing plate, apolarizing axis of the reflective polarizing plate 14 and a slow axis ofthe quarter wave plate 15 are arranged so as to have an angle of 45° or135° between them. Also, in a case of using the linear reflectivepolarizing plate, the transmission axis of the reflective polarizingplate 14 and a transmission axis of the polarizing plate 16 are arrangedso as to be parallel to each other.

By this structure, similarly to Embodiment Mode 1, external light whichenters the display device is absorbed in the polarizing plate 16, andthe external light is not emitted to outside again. Thus, reflection ofan outside image can be suppressed.

On the other hand, similarly to Embodiment Mode 1, light emitted in thelight-emitting layer 12 is repeatedly reflected between the reflectivepolarizing plate 14 and the reflective electrode 13; accordingly, thelight emitted in the light-emitting layer 12 can be efficiently emitted.Therefore, a light emission component which has not conventionally beenable to be used can be utilized effectively, and enhancement ofbrightness of a display image can be attempted. In this embodiment mode,since the light is repeatedly reflected between the reflectivepolarizing plate 14 and the reflective electrode 13 through the prismlayer 201, the polarizing axis can be efficiently displaced, andextraction efficiency of the light emitted in the light-emitting layer12 can be more enhanced. One or a plurality of prism layers 201 may beprovided as long as the prism layer has a function of not onlyconverging light emission but also changing a direction or a state ofpolarization which is repeatedly reflected between the reflectivepolarizing plate 14 and the reflective electrode 13.

In the display device of this embodiment mode, reflection of an outsideimage when external light is reflected on the reflective polarizingplate 14 can be suppressed, and display characteristics of an image canbe improved. In addition, light emitted in the light-emitting layer 12can be extracted efficiently, and improvement in brightness of a displayimage can be attempted.

Embodiment Mode 3

In this embodiment mode, a case where a quarter wave plate is providedbetween a reflective polarizing plate 14 and a substrate 100 will beexplained. It is to be noted that, in FIG. 3, the same portions as thosein FIGS. 1A and 1B are denoted by the same reference numerals, and theexplanation is omitted. In FIG. 3, part of a display device of thisembodiment mode is shown.

In the display device of this embodiment mode, as shown in FIG. 3, atransparent electrode 11, a light-emitting layer 12, and a reflectiveelectrode 13 are stacked over the substrate 100, and a quarter waveplate 301 (referred to as a first quarter wave plate), the reflectivepolarizing plate 14, a quarter wave plate 15 (referred to as a secondquarter wave plate), and a polarizing plate 16 are stacked over asurface of the substrate 100, which is opposite to the surface providedwith the transparent electrode 11. In other words, the display devicehas a structure in which the reflective electrode 13, the light-emittinglayer 12, the transparent electrode 11, the substrate 100, the quarterwave plate 301, the reflective polarizing plate 14, the quarter waveplate 15, and the polarizing plate 16 are sequentially stacked.

In this embodiment mode, in a case of using a linear polarizationreflective polarizing plate as the reflective polarizing plate, apolarizing axis of the reflective polarizing plate 14 and a polarizingaxis of the first quarter wave plate 301 are arranged so as to have anangle of 45° or 135° between them. In addition, in a case of using thelinear polarization reflective polarizing plate as the reflectivepolarizing plate 14, a transmission axis of the reflective polarizingplate 14 and a transmission axis of the second quarter wave plate 15 arearranged so as to have an angle of 45° or 135° between them. Moreover,in a case of using the linear polarization reflective polarizing plate,the transmission axis of the reflective polarizing plate 14 and atransmission axis of the polarizing plate 16 are arranged so as to beparallel to each other.

Here, a case where the reflective polarizing plate is the linearpolarization reflective polarizing plate is explained. First, apolarization component (referred to as first polarization) of externallight which enters from an observation surface of a display device,i.e., an upper side of the polarizing plate 16, which is parallel to anabsorption axis of the polarizing plate 16, is absorbed in thepolarizing plate 16, and second polarization which is parallel to thetransmission axis of the polarizing plate 16 enters the display device.The second polarization is converted to right-hand or left-hand circularpolarization by passing through the second quarter wave plate 15. Acomponent of the second polarization, which does not coincide with thetransmission axis of the reflective polarizing plate 14, is reflected onthe reflective polarizing plate 14, and is absorbed without passingthrough the polarizing plate 16, similarly to Embodiment Mode 1, and acomponent of external light, which has entered the display device is notemitted outside again.

A polarization component of the second polarization, which coincideswith the transmission axis of the reflective polarizing plate 14, passesthrough the reflective polarizing plate 14. Thereafter, the polarizationcomponent is converted to right-hand or left-hand circular polarizationat the first quarter wave plate 301, reflected on the reflectiveelectrode 13, and returns toward the first quarter wave plate 301. Sincethe circular polarization reflected on the reflective electrode 13reverses the polarization direction, the polarization which has passedthrough the first quarter wave plate 301 is reflected on the reflectivepolarizing plate 14. The reflected light passes through the firstquarter wave plate 301 again, becomes circular polarization, and isreflected on the reflective electrode 13 again. The circularpolarization passes through the quarter wave plate again; accordingly,the circular polarization becomes linear polarization which coincideswith the transmission axis of the reflective polarizing plate 14, isconverted to circular polarization at the second quarter wave plate 15,and a component which coincides with the absorption axis of thepolarizing plate 16 is absorbed. Although part of the component isemitted, light which is attenuated in the display device is emittedfinally. Thus, reflection of an outside image can be suppressed to adegree which does not cause a problem in use.

On the other hand, light emitted in the light-emitting layer 12 is firstconverted to circular polarization or linear polarization at the firstquarter wave plate 301. A polarization component of the convertedcomponents, which is parallel to the transmission axis of the reflectivepolarizing plate 14, passes through the reflective polarizing plate 14,the quarter wave plate 15, and the polarizing plate 16, and emitted fromthe display device. The other polarization component is reflected on thereflective polarizing plate 14 to return in a direction of the firstquarter wave plate 301, and is converted to right-hand or left-handcircular polarization. The right-hand or left-hand circular polarizationis reflected on the reflective electrode 13, and enters the firstquarter wave plate 301 again as circular polarization in which thepolarization direction is reversed. Then, the right-hand or left-handcircular polarization is converted, at the first quarter wave plate 301,to polarization having a polarizing axis which is parallel to thereflective polarizing plate 14, passes through the polarizing plate 16,and is emitted from the display device. Therefore, a light emissioncomponent from the light-emitting layer 12 which has not conventionallybeen able to be used can be utilized efficiently, and enhancement ofbrightness of a display image can be attempted.

In addition, a case where the reflective polarizing plate is a circularpolarization reflective polarizing plate is explained. Here, a casewhere the reflective polarizing plate 14 has functions of transmittingleft-hand circular polarization and reflecting right-hand circularpolarization is explained. First, a polarizing component (referred to asfirst polarization) of external light which enters from an observationsurface of a display device, i.e., an upper side of the polarizing plate16, which is parallel to an absorption axis of the polarizing plate 16,is absorbed in the polarizing plate 16, and second polarization which isparallel to the transmission axis of the polarizing plate 16 enters thedisplay device. The second polarization passes through the quarter waveplate 15, and is converted to right-hand circular polarization, forexample; accordingly, similarly to Embodiment Mode 1, the secondpolarization is absorbed without passing through the polarizing plate16, and a component of external light which enters the display device isnot emitted outside again. Thus, reflection of an outside image can besuppressed.

On the other hand, light emitted in the light-emitting layer 12 is firstconverted to circular polarization, elliptic polarization, or linearpolarization at the first quarter wave plate 301. One circularpolarization component of the converted components passes through thereflective polarizing plate 14, the quarter wave plate 15, and thepolarizing plate 16, and is emitted from the display device. The otherpolarization component is reflected on the reflective polarizing plate14, returns in a direction of the light-emitting layer 12 through thefirst quarter wave plate 301, is reflected on the reflective electrode13, and enters the reflective polarizing plate 14 again. Here,polarization which does not pass through the reflective polarizing plate14 is repeatedly reflected between the reflective polarizing plate 14and the reflective electrode 13 through the first quarter wave plate301. By the repeated reflection, a polarizing axis is displaced. Therepeatedly reflected light passes through the reflective polarizingplate 14, the quarter wave plate 15, and the polarizing plate 16, and isemitted from the display device. Therefore, a light emission componentwhich has not conventionally been able to be used can be utilizedeffectively, and enhancement of brightness of a display image can beattempted.

In this embodiment mode, a prism layer, a scattering layer, or a layerin which the prism layer and the scattering layer are combined may alsobe provided between the substrate 100 and the first quarter wave plate301.

In the display device of this embodiment mode, reflection of an outsideimage when external light is reflected on the reflective polarizingplate 14 can be suppressed, and display characteristics of an image canbe improved. Also, by providing the quarter wave plate between thereflective polarizing plate 14 and the substrate 100, external lightwhich passes through the reflective polarizing plate 14 can be preventedfrom returning to outside of the display device again. Furthermore, thereflection of an outside image can be suppressed, and displaycharacteristics of an image can be improved. Moreover, light emitted inthe light-emitting layer 12 can be extracted efficiently, andimprovement in brightness of a display image can be attempted.

Embodiment Mode 4

In this embodiment mode, a display device in which an extractiondirection of light emission from a light-emitting layer is differentfrom those in Embodiment Modes 1 to 3 will be explained. It is to benoted that, in FIGS. 4A and 4B, the same portions as those in FIGS. 1Aand 1B are denoted by the same reference numerals, and the explanationis omitted. In FIGS. 4A and 4B, part of a display device of thisembodiment mode is shown.

As shown in FIG. 4A, the display device of this embodiment mode has astructure in which a reflective electrode 4001, a light-emitting layer12, a transparent electrode 4002, a reflective polarizing plate 14, aquarter wave plate 15, and a polarizing plate 16 are sequentiallystacked over a substrate 100. In this embodiment mode, a structure isemployed, in which light emission from the light-emitting layer 12 isextracted from the transparent electrode 4002 side (an opposite side ofthe substrate 100). It is to be noted that, in this embodiment mode, asingle layer or a stacked layer of an insulating film may be providedbetween the transparent electrode 4002 and the reflective polarizingplate 14. In addition, a scattering layer such as a prism may also beprovided between the transparent electrode 4002 and the reflectivepolarizing plate 14. Further alternatively, a quarter wave plate may beprovided.

In the structure shown in FIG. 4A, since light emission from thelight-emitting layer 12 is not extracted through the substrate 100, thesubstrate 100 is not necessarily a transparent substrate. For example, aceramic substrate, a silicon substrate, a metal substrate, a stainlesssteel substrate, or the like may be used.

By the structure shown in FIG. 4A, external light which enters thedisplay device from the polarizing plate 16 side is absorbed in thepolarizing plate 16; accordingly, reflection of an outside image can besuppressed.

On the other hand, light emitted in the light-emitting layer 12 isrepeatedly reflected between the reflective polarizing plate 14 and thereflective electrode 4001. Accordingly, a light emission component fromthe light-emitting layer 12, which has not conventionally been able tobe used, can be utilized effectively, and enhancement of brightness of adisplay image can be attempted.

In the display device shown in FIG. 4A, reflection of an outside imagewhen external light is reflected on the reflective polarizing plate 14can be suppressed, and display characteristics of an image can beimproved. Moreover, light emitted in the light-emitting layer 12 can beextracted efficiently, and decrease in brightness of a display image canbe suppressed.

A transparent electrode 4003 may be provided instead of the reflectiveelectrode 4001 of FIG. 4A (FIG. 4B). In that case, a reflectivepolarizing plate, a quarter wave plate, and a polarizing plate arepreferably provided at each side of the substrate 100. In other words,as shown in FIG. 4B, the display device has a structure in which a firstpolarizing plate 4004, a first quarter wave plate 4005, a firstreflective polarizing plate 4006, the substrate 100, a first transparentelectrode 4003, the light-emitting layer 12, a second transparentelectrode 4002, a second reflective polarizing plate 14, a secondquarter wave plate 15, and a second polarizing plate 16 are sequentiallystacked. In this embodiment mode, light emission from the light-emittinglayer 12 is extracted from the transparent electrode 4002 side and thetransparent electrode 4003 side. In other words, light is extracted fromtwo directions which are the substrate 100 side and the opposite side ofthe substrate 100.

It is to be noted that, in this embodiment mode, a single layer or astacked layer of an insulating film may be provided between thetransparent electrode 4002 and the reflective polarizing plate 14. Inaddition, between the transparent electrode 4002 and the reflectivepolarizing plate 14, a scattering layer such as a prism may also beprovided, or further, a quarter wave plate may be provided.

By the structure shown in FIG. 4B, external light which enters thedisplay device from the first polarizing plate 4004 side or the secondpolarizing plate 16 side is absorbed in the first polarizing plate 4004or the second polarizing plate 16, and is not emitted outside again.Thus, reflection of an outside image can be suppressed. Further, in acase of using a linear polarization reflective polarizing plate as thereflective polarizing plate, it is preferable that the first polarizingplate and the second polarizing plate be arranged so that theirtransmission axes cross at right angles. By making the transmission axescross at right angles, light of light emitted from the light-emittinglayer 12 to go toward one light emission side, which is reflected on thefirst reflective polarizing plate 4006 or the second reflectivepolarizing plate 14 and returns, can be efficiently extracted from anopposite light emission surface. In addition, in a case of using acircular polarization reflective polarizing plate as the reflectivepolarizing plate, it is preferable that the first reflective polarizingplate and the second reflective polarizing plate be arranged so thattheir spiral rotation directions are opposite to each other. By makingthe rotation directions opposite to each other, light emission from thelight-emitting layer 12 can be extracted efficiently.

The polarizing plates 16 and 4004 each have functions of transmittinglinear polarization having a vibrating surface which is parallel to thepolarizing axis and absorbing linear polarization having the vibratingsurface which crosses the polarizing axis at right angles.

In this embodiment mode, in a case of using the linear polarizationreflective polarizing plate as the reflective polarizing plate, apolarizing axis of the reflective polarizing plate 14 and a slow axis ofthe quarter wave plate 15 are arranged so as to have an angle of 45° or135° between them, and a polarizing axis of the reflective polarizingplate 4006 and a slow axis of the quarter wave plate 4005 are arrangedso as to have an angle of 45° or 135° between them.

As the transparent electrodes 4002 and 4003 of FIGS. 4A and 4B, thefollowing can be used: indium tin oxide (ITO), indium tin oxidecontaining silicon oxide (ITSO), zinc oxide (ZnO), indium zinc oxide(IZO) formed using a target in which 2 to 20 wt % of zinc oxide (ZnO) isfurther mixed with indium oxide containing silicon oxide, zinc oxidecontaining gallium (GZO), tin oxide (SnO₂), indium oxide (In₂O₃), or thelike.

It is preferable to use highly reflective metal as the reflectiveelectrode 4001 of FIG. 4A. Aluminum (Al), silver (Ag), an AlLi alloy ora MgAg alloy which are alloys containing the metal, and the like can beused. In addition, the reflective electrode 4001 may be formed of astacked layer of the highly reflective metal and other electrodematerial. By forming a thin film (e.g., approximately 5 nm) of alkalimetal or alkaline earth metal and stacking the thin film with the highlyreflective metal, an electron injecting property can be enhanced.

In the display device of this embodiment mode, reflection of an outsideimage when external light is reflected on reflective polarizing platecan be suppressed, and display characteristics of an image can beimproved. In addition, light emitted in the light-emitting layer 12 canbe extracted efficiently, and improvement in brightness of a displayimage can be attempted.

Embodiment Mode 5

In this embodiment mode, a manufacturing process of a display devicehaving a thin film transistor (TFT) will be explained. It is to be notedthat, although a structure in which light emission from a light-emittinglayer 12 is extracted only from a substrate 100 side is explained inthis embodiment mode, the present invention is not limited thereto. Astructure in which light emission is extracted from a side opposite tothe substrate 100 may be employed. A structure in which light emissionis extracted from two directions which are the substrate 100 side andthe side opposite to the substrate 100 may also be employed.

First, as shown in FIG. 5A, the substrate 100 is prepared. As thesubstrate 100, a glass substrate of barium borosilicate glass, aluminoborosilicate glass, or the like, a quartz substrate, a ceramicsubstrate, or the like can be used, for example. Although a substratemade of a flexible synthetic resin such as plastic generally tends tohave lower allowable temperature limit than that of the above substrate,the substrate made of a flexible synthetic resin can be used as long asthe substrate can endure a processing temperature in a manufacturingprocess. A surface of the substrate 100 may be planarized by polishingby a CMP method or the like.

Next, a base film 101 is formed over the substrate 100 (FIG. 5A). In acase of using glass for the substrate 100, the base film 101 can preventalkali metal or alkaline earth metal contained in the substrate, such asNa from diffusing in a semiconductor film and having an adverse effecton characteristics of a semiconductor element. Therefore, the base film101 is formed using an insulating film of silicon oxide, siliconnitride, silicon nitride oxide, or the like, which can suppressdiffusion of alkali metal or alkaline earth metal in the semiconductorfilm. In this embodiment mode, a silicon nitride oxide film is formed tohave a thickness of 10 to 400 nm by a plasma CVD method. It is to benoted that the silicon nitride oxide film can be formed by known methodssuch as a sputtering method and a decompression CVD method other than aplasma CVD method. In addition, although the base film 101 is formed ofa single layer in this embodiment mode, the base film 101 may be formedof two or more layers.

In a case of using a substrate in which alkali metal or alkaline earthmetal is somewhat contained, such as a glass substrate or a plasticsubstrate, it is effective to provide the base film 101 from theviewpoint of preventing impurity diffusion. However, when impuritydiffusion is not such a big problem, such as a case of using a quartzsubstrate, the base film 101 is not necessarily provided.

Then, an amorphous semiconductor film 102 is formed over the base film101. The amorphous semiconductor film 102 may be formed to have athickness of 25 to 80 nm by using silicon or a material containingsilicon as its main component (e.g., Si_(x)Ge_(1-x) or the like). As amanufacturing method, known methods such as a sputtering method, adecompression CVD method, and a plasma CVD method can be used.

Subsequently, the amorphous semiconductor film 102 is crystallized. Theamorphous semiconductor film 102 is crystallized by a lasercrystallization method, a thermal crystallization method using RTA orfurnace anneal, a thermal crystallization method using acrystallization-promoting metal element (FIG. 5A).

Next, island-shaped semiconductor films 102 a to 102 c are formed byetching the crystalline semiconductor film. Then, a gate insulating film103 is formed so as to cover the island-shaped semiconductor films 102 ato 102 c (FIG. 5B). The gate insulating film 103 can be formed of asingle layer or a stacked layer by using silicon oxide, silicon nitride,silicon nitride oxide, or the like, for example. The gate insulatingfilm 103 can be formed by a plasma CVD method, a sputtering method, orthe like. Here, the gate insulating film 102 is formed using aninsulating film containing silicon to have a thickness of 30 to 200 nmby using a sputtering method.

Then, a gate electrode is formed over the gate insulating film 103. Inthis embodiment mode, the gate electrode has a two-layer structure of afirst conductive film and a second conductive film. A tantalum nitride(TaN) film is formed as each of first conductive layers 104 a to 104 c,and a tungsten (W) film is formed thereover as each of second conductivelayers 105 a to 105 c (FIG. 5C). Both the tantalum nitride (TaN) filmand the tungsten (W) film may be formed by a sputtering method. Thetantalum nitride (TaN) film is formed using a target of tantalum in anitrogen atmosphere and the tungsten (W) film may be formed using atarget of tungsten.

It is to be noted that, although the first conductive layer is formed ofTaN and the second conductive layer is formed of W in this embodimentmode, the present invention is not limited thereto. Both the firstconductive layer and the second conductive layer may be formed of anelement selected from Ta, W, Ti, Mo, Al, Cu, Cr, and Nd; an alloymaterial containing the above element as its main component; or acompound material thereof. In addition, a semiconductor film typified bya polycrystalline silicon film doped with an impurity element such asphosphorus may also be used. Moreover, an AgPdCu alloy may also be used.A combination thereof may be appropriately selected. The firstconductive layer may be formed to have a thickness of 20 to 100 nm, andthe second conductive layer may be formed to have a thickness of 100 to400 nm. Although the gate electrode has a stacked structure of twolayers in this embodiment, a one-layer structure or a stacked structureof three or more layers may also be used.

Next, impurities imparting n-type or p-type conductivity is selectivelyadded to the semiconductor films 102 a to 102 c by using the gateelectrode or a resist which is etched as a mask so that a source region,a drain region, an LDD region, and the like are formed.

Next, a resist mask is removed, and a first passivation film 106 isformed (FIG. 5D). As the first passivation film 106, an insulating filmcontaining silicon is formed to have a thickness of 100 to 200 nm. Thefirst passivation film 106 may be formed by using a plasma CVD methodand a sputtering method. In this embodiment mode, a silicon oxynitridefilm is formed by a plasma CVD method. In a case of using the siliconoxynitride film, a silicon oxynitride film formed of SiH₄, N₂O, and NH₃or a silicon oxynitride film formed of SiH₄ and N₂O may be formed by aplasma CVD method. Manufacturing conditions in this case are as follows:a reaction pressure is set to be 20 to 200 Pa, a substrate temperatureis set to be 300 to 400° C., and a high-frequency (60 MHz) power densityis set to be 0.1 to 1.0 W/cm². In addition, a silicon oxynitride hydridefilm formed of SiH₄, N₂O, and H₂ may also be applied as the firstpassivation film. It is needless to say that the first passivation film106 is not limited to the single layer of the silicon oxynitride film asin this embodiment mode, and a single layer of other insulating filmcontaining silicon or a stacked layer thereof may also be used.

Thereafter, a laser annealing method is preferably performed to restorecrystallinity of the semiconductor film and activate an impurity elementadded to the semiconductor film 106. In addition, by performing heattreatment after forming the first passivation film 106, hydrogenation ofthe semiconductor film can be performed concurrently with activationtreatment. The hydrogenation is performed to terminate a dangling bondof the semiconductor film by hydrogen contained in the first passivationfilm 106. Here, the hydrogenation is performed by using a SiNO film forthe passivation film 106 at a temperature of 410° C. under an nitrogenatmosphere.

Alternatively, heat treatment may be performed before forming the firstpassivation film 106. However, in a case where materials for forming thefirst conductive layers 104 a to 104 c and the second conductive layers105 a to 105 c are weak against heat, heat treatment is preferablyperformed after forming the first passivation film 106 in order toprotect a wiring or the like as in this embodiment mode. Furthermore, inthis case, since the first passivation film is not formed yet,hydrogenation obviously cannot be performed using hydrogen contained inthe passivation film.

In this case, hydrogenation may be performed by means using hydrogenwhich is excited by plasma (plasma hydrogenation), or hydrogenation maybe performed by heat treatment in an atmosphere containing hydrogen of 3to 100% at a temperature of 300 to 450° C. for 1 to 12 hours. In thismanner, TFTs 401 to 403 having the semiconductor film, the gateinsulating film, and the gate electrode can be obtained. It is to benoted that the structure of the TFTs 401 to 403 is not limited to theone in this embodiment mode.

Next, a first interlayer insulating film 107 is formed over the firstpassivation film 106 (FIG. 5E). An inorganic insulating film or anorganic insulating film can be used as the first interlayer insulatingfilm 107. As the inorganic insulating film, a silicon oxide film formedby a CVD method or a silicon oxide film coated by an SOG (spin on glass)method can be used. As the organic insulating film, a film formed ofpolyimide, polyamide, BCB (benzocyclobutene), acrylic, a positivephotosensitive organic resin, a negative photosensitive organic resin,or the like can be used. In addition, a stacked structure of an acrylicfilm and a silicon oxynitride film may also be used.

Siloxane in which a skeleton structure is formed by a bond of silicon(Si) and oxygen (O) can be used as a material for the interlayerinsulating film. As a substituent of siloxane, an organic groupcontaining at least hydrogen (e.g., an alkyl group, aromatichydrocarbon, or the like) is used. Furthermore, as a substituent, afluoro group may also be used. Alternatively, as a substituent, both ofan organic group containing at least hydrogen and a fluoro group may beused.

Siloxane based polymer, according to its structure, can be classifiedinto silica glass, alkylsiloxane polymer, alkylsilsesquioxane polymer,hydrogen silsesquioxane polymer, hydrogen alkylsilsesquioxane polymer,or the like, for example. In addition, the interlayer insulating filmmay be formed using a material containing polymer having a Si—N bond(polysilazane).

By using the above materials, an interlayer insulating film havingenough insulating property and planarizing property can be obtained evenwhen the film is formed to be thin. In addition, the above materialshave high heat resistance; therefore, an interlayer insulating filmwhich can endure reflow treatment that is performed for a multilayerwiring can be obtained. Furthermore, the above materials have a lowhygroscopic property; therefore, an interlayer insulating film with asmall amount of dehydration can be formed.

In this embodiment mode, siloxane-based polymer is used for forming thefirst interlayer insulating film 107. Concavity and convexity due toTFTs formed over the substrate can be reduced by the first interlayerinsulating film 107, and planarization can be performed. In particular,since the first interlayer insulating film 107 is used mainly for thepurpose of planarization, an insulating film using an easily-planarizedmaterial is preferably used. In addition, silicon oxide containingnitrogen can be used for the first interlayer insulating film, in whichcase the first passivation film is not necessary to be provided.

Thereafter, a second passivation film formed of a silicon nitride oxidefilm or the like may be formed over the first interlayer insulating film107. The second passivation film may be formed to have a thickness ofapproximately 10 to 200 nm. The second passivation film can preventmoisture from entering and leaving the first interlayer insulating film107. Besides the silicon nitride oxide film, a silicon nitride film, analuminum nitride film, an aluminum oxynitride film, a diamond likecarbon (DLC) film, and a carbon nitride (CN) film can be used for thesecond passivation film in the same manner.

A film formed using an RF sputtering method has high density and anexcellent barrier property. In a case of forming a silicon oxynitridefilm for example, the silicon oxynitride film is formed by RF sputteringunder conditions where Si is used as a target, N₂, Ar, and N₂O areflowed with the gas-flow ratio of 31:5:4, respectively, the pressure isset to be 0.4 Pa, and the power is set to be 3,000 W. In addition, in acase of forming a silicon nitride film for example, the silicon nitridefilm is formed by RF sputtering under conditions where Si is used as atarget, N₂ and Ar in a chamber are flowed with the gas-flow ratio of1:1, the pressure is set to be 0.8 Pa, the power is set to be 3,000 W,and a film-forming temperature is set to be 215° C.

Then, the first interlayer insulating film 107 and the first passivationfilm 106 are etched to form contact holes reaching a source region and adrain region. Subsequently, wirings 108 a to 108 f each of which iselectrically connected to the source region or the drain region in eachTFT are formed (FIG. 6A). As the wirings 108 a to 108 f, a single layerstructure or a stacked layer structure formed of one element selectedfrom Al, Ni, W, Mo, Ti, Pt, Cu, Ta, Au, and Mn, or an alloy containing aplurality of the elements can be used. Here, the wirings 108 a to 108 fare preferably formed of a metal film containing Al. In this embodimentmode, a stacked film formed of a Ti film and an alloy film containing Aland Ti is formed by etching. It is needless to say that the structure isnot limited to a two-layer structure, and a single layer structure and astacked structure of three or more layers may be used. In addition, thematerials for the wirings are not limited to a stacked film including Aland Ti. For example, the wirings may be formed by forming an Al film ora Cu film over a TaN film and etching a stacked film in which a Ti filmis further formed.

Next, a second interlayer insulating film 109 is formed so as to coverthe wirings 108 a to 108 f. A similar material to that described abovefor the first interlayer insulating film can be used for the secondinterlayer insulating film. In this embodiment mode, siloxane-basedpolymer is used for the second interlayer insulating film 109. Sincesiloxane-based polymer has high heat resistance, an interlayerinsulating film which can endure reflow treatment that is performed fora multilayer wiring can be obtained.

Subsequently, the second interlayer insulating film 109 is selectivelyetched to form a contact hole. After that, a wiring 111 for beingconnected to the wiring 108 f is formed. In addition, a pixel electrode112 a is formed at the same time as the wiring 111 (FIG. 6B). The wiring111 and the pixel electrode 112 a can be formed using a single layer ora stacked structure formed of one element selected from Al, Ni, W, Mo,Ti, Pt, Cu, Ta, Au, and Mn, or an alloy containing a plurality of theelements. In this embodiment mode, an Al alloy may be used, and thewiring 111 and the pixel electrode 112 a are formed by Al—Ni—C.

Next, a pixel electrode 112 b is formed over the second interlayerinsulating film 109, the wiring 111, and the pixel electrode 112 a (FIG.6C). The pixel electrode 112 b is formed so as to be in contact with thesecond interlayer insulating film 109 at least in a region 119 where thepixel electrode 112 b is not overlapped with the wiring 111 and thepixel electrode 112 a. In this embodiment mode, the pixel electrode 112a and the pixel electrode 112 b are formed of a transparent conductivefilm. For example, indium tin oxide (ITO), zinc oxide (ZnO), indium zincoxide (IZO), zinc oxide added with gallium (GZO), and otherlight-transmitting oxide conductive material can be used. Indium tinoxide (ITO) and indium tin oxide containing silicon oxide (ITSO), orindium zinc oxide formed using a target in which 2 to 20 wt % of zincoxide (ZnO) is mixed with indium oxide containing silicon oxide may beused.

Then, an insulating film (a partition wall or a bank) 116 is formed soas to cover ends of the pixel electrodes 112 a and 112 b, and alight-emitting layer 114 is formed so as to be in contact with the pixelelectrode 112 b. The light-emitting layer 114 contains a light-emittingsubstance. For example, the light-emitting layer 114 has a holeinjecting layer 701, a hole transporting layer 702, a light-emittinglayer 703, an electron transporting layer 704, and an electron injectinglayer 705 (FIG. 7). It is to be noted that the structure of thelight-emitting layer 114 is not necessarily limited thereto. Thelight-emitting layer 114 includes a single layer or stacked structurehaving at least a light-emitting layer. FIG. 7 shows a schematiccross-sectional view of the light-emitting layer 114 having the holeinjecting layer 701, the hole transporting layer 702, the light-emittinglayer 703, the electron transporting layer 704, and the electroninjecting layer 705, which are interposed between the pixel electrode112 b and an electrode 115.

Materials having a hole transporting property, relatively smallionization potential, and a high hole injecting property are desirablyused for the hole injecting layer 701. The materials are classifiedbroadly into metal oxide, a low molecular organic compound, and a highmolecular organic compound. As the metal oxide, vanadium oxide,molybdenum oxide, ruthenium oxide, aluminum oxide, or the like can beused, for example. As the low molecular compound, starburst aminetypified by m-MTDATA; metallophthalocyanine typified by copperphthalocyanine (abbreviation: Cu—Pc); phthalocyanine (abbreviation:H₂—Pc); a 2,3-dioxyethylene thiophene derivative; or the like can beused. A film formed by co-evaporation of the low molecular weightorganic compound and the above metal oxide may also be used. As the highmolecular weight organic compound, for example, high molecule such aspolyaniline (abbreviation: PAni), polyvinyl carbazole (abbreviation:PVK), or a polythiophene derivative can be used. Polyethylenedioxythiophene (abbreviation: PEDOT), which is one of polythiophenederivatives, doped with polystyrene sulfonate (abbreviation: PSS). Inaddition, a mixture of a benzoxazole derivative and any one or more ofTCQn, FeCl₃, C₆₀ and F₄TCNQ may be used.

Known materials having a high hole transporting property and lowcrystallinity are desirably used for the hole transporting layer 702.For example, aromatic amine-based compounds (that is, compounds having abond of benzene ring-nitrogen) are preferable, and there are4,4′-bis[N-(3-methylphenyl)-N-phenylamino]biphenyl (abbreviation: TPD);a derivative thereof such as4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation: α-NPD);and the like. Besides, starburst aromatic amine compounds such as4,4′,4″-tris(N,N-diphenylamino)triphenylamine (abbreviation: TDATA) andMTDATA can be used. In addition, 4,4′4″-tris(N-carbazolyl)triphenylamine(abbreviation: TCTA) may also be used. Moreover, as a high molecularmaterial, poly(vinylcarbazole) or the like showing a favorable holetransporting property can be used.

Materials having high ionization potential and a large bandgap aredesirably used for the light-emitting layer 703. For example, metalcomplexes such as tris(8-quinolinolato)aluminum (abbreviation: Alq₃),tris(4-methyl-8-quinolinolato)aluminum (abbreviation: Almq₃),bis(10-hydroxybenzo[h]-quinolinato)beryllium (abbreviation: BeBq₂),bis(2-methyl-8-quinolinolato)-(4-hydroxy-biphenyl)aluminum(abbreviation: BAlq), bis[2-(2-hydroxyphenyl)-benzoxazolato]zinc(abbreviation: Zn(BOX)₂), andbis[2-(2-hydroxyphenyl)-benzothiazolato]zinc (abbreviation: Zn(BTZ)₂)canbe used. In addition, various fluorescent pigments (such as a coumarinderivative, a quinacridone derivative, rubrene, 4,4-dicyanomethylene, a1-pyrone derivative, a stilbene derivative, and various condensedaromatic compounds) can also be used. Moreover, phosphorescent materialssuch as a platinum octaethylporphyrin complex, atris(phenylpyridine)iridium complex, and atris(benzylideneacetonate)phenanthrene europium complex can be used.

As host materials used for the light-emitting layer 703, holetransporting materials or electron transporting materials typified bythe above-described examples can be used. Besides, bipolar materialssuch as 4,4′-N,N′-dicarbazolyl biphenyl (abbreviation: CBP) can also beused.

Materials having a high electron transporting property are desirablyused for the electron transporting layer 704. For example, a metalcomplex having a quinoline skeleton or a benzoquinoline skeletontypified by Alq₃, a mixed ligand complex thereof, and the like can beused. Specifically, metal complexes such as Alq₃, Almq₃, BeBq₂, BAlq,Zn(BOX)₂, and Zn(BTZ)₂ are given. Besides the metal complexes,oxadiazole derivatives such as2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviation:PBD) and 1,3-bis[5-(p-tert-buthylphenyl)-1,3,4-oxadiazol-2-yl]benzene(abbreviation: OXD-7); triazole derivatives such as3-(4-tert-buthylphenyl)-4-phenyl-5-(4-biphenylyl)-1,2,4-triazole(abbreviation: TAZ) and3-(4-tert-buthylphenyl)-4-(4-ethylphenyl)-5-(4-biphenylyl)-1,2,4-triazole(abbreviation: p-EtTAZ); imidazole derivatives such as TPBI; andphenanthroline derivatives such as bathophenanthroline (abbreviation:BPhen) and bathocuproin (abbreviation: BCP) can be used.

Materials having a high electron injecting property are desirably usedfor the electron injecting layer 705. For example, an ultrathin film ofan insulator such as alkali metal halide such as LiF or CsF; alkalineearth halide such as CaF2; alkali metal oxide such as Li₂O is commonlyused. In addition, alkali metal complexes such as lithiumacetylacetonate(abbreviation: Li(acac)) and 8-quinolinolato-lithium (abbreviation: Liq)are also effective. Moreover, one or a plurality of metal oxide such asmolybdenum oxide (MoOx), vanadium oxide (VOx), ruthenium oxide (RuOx),or tungsten oxide (WOx); a benzoxazole derivative; alkali metal;alkaline earth metal; and transition metal may be used. Titanium oxidemay also be used.

It is to be noted that the light-emitting layer 114 does not necessarilyhave all of these layers. In this embodiment mode, it is acceptable aslong as the light-emitting layer 114 has at least the light-emittinglayer 703. Light emission is not always extracted only from thelight-emitting layer 703, and there is a case where light-emission canbe obtained from layers other than the light-emitting layer 703,depending on a combination of materials used for other layers. Inaddition, a hole blocking layer may be provided between thelight-emitting layer 703 and the electron transporting layer 704.

It is to be noted that there is a case where, depending on the color,lower voltage driving and higher reliability can be achieved by using aphosphorescent material than using a fluorescent material. In a case ofperforming full color display using light emitting elementscorresponding to the three primary colors, the light emitting elementsof the respective colors may be made to have the same deteriorationlevel by combining a light emitting element using a fluorescent materialand a light emitting element using a phosphorescent material.

In the light-emitting layer 114, a material that is resistant to etchingis used for a layer which is closest to the electrode 115 (in thisembodiment mode, the electron injecting layer 705). Thus, when theelectrode 115 is formed over the light-emitting layer 114 by sputtering,sputtering damages to the layer which is closest to the electrode 115(in this embodiment mode, the electron injecting layer 705) can bereduced. For example, a metal oxide such as molybdenum oxide (MoOx),vanadium oxide (VOx), ruthenium oxide (RuOx), or tungsten oxide (WOx);or a benzoxazole derivative can be used as the material that isresistant to etching. The material is preferably formed by anevaporation method. According to the above structure, even when theelectrode 115 is formed by a sputtering method, sputtering damages to alayer containing an organic matter included in the light-emitting layer114 can be suppressed, and the scope of material choices for forming theelectrode 115 is expanded.

Thereafter, the electrode 115 is formed so as to be in contact with thelight-emitting layer 114 (FIG. 6D). In this embodiment mode, theelectrode 115 is formed of a reflective conductive film. Since theelectrode 115 is used as a cathode, metal, an alloy, and anelectro-conductive compound having low work function, and a mixture ofthese are used. For example, rare earth metal such as Yb or Er can beused in addition to alkali metal such as Li or Cs; alkaline earth metalsuch as Mg, Ca, or Sr; an alloy containing these (Mg:Ag, Al:Li, Mg:In,or the like); and a compound of these (CaF₂ or CaN). Moreover, in a caseof providing the electron injecting layer, other conductive film of Alor the like can also be used.

After that, a protective layer may be formed over the electrode 115 byan evaporation method or a sputtering method using a mask. Theprotective layer protects the electrode 115. It is to be noted that theprotective layer is not necessarily provided.

Then, a sealing substrate 601 is bonded by a sealant to seal thelight-emitting element. A circumference of a display region issurrounded by the sealant so that the display device is sealed with thesubstrate 100 and the sealing substrate 601. Further, the regionsurrounded by the sealant is filled with a filler 602. Alternatively,the region surrounded by the sealant is filled with dried inert gas(FIG. 6D).

Next, a reflective polarizing plate 14, a quarter wave plate 15, and apolarizing plate 16 are sequentially stacked over a surface of thesubstrate 100, which is opposite to the surface over which the electrode15 is formed (FIG. 8). In this embodiment mode, in a case of using alinear polarization reflective polarizing plate as the reflectivepolarizing plate, a transmission axis of the reflective polarizing plate14 and a delay axis of the quarter wave plate 15 are arranged so as tohave an angle of 45° or 135° between them.

In the display device having the above structure, by applying voltagebetween the pixel electrode 112 b and the electrode 115 and supplyingforward bias current to the light-emitting layer 114, light is emittedfrom the light-emitting layer 114 and the light can be extracted fromthe pixel electrode 112 b side.

According to the above steps, the display device shown in FIG. 8 can bemanufactured. In the display device of this embodiment mode, reflectionof an outside image when external light is reflected on the reflectivepolarizing plate 14 can be suppressed and display characteristics of animage can be improved. In addition, light emitted in the light-emittinglayer 114 can be extracted efficiently, and improvement in brightness ofa display image can be attempted.

Embodiment Mode 6

In this embodiment mode, a panel of the display device shown inEmbodiment Mode 5 will be explained with reference to FIGS. 9A and 9B.

A display region 51 having a plurality of pixels each including alight-emitting element, gate drivers 52 and 53, a source driver 54, anda connection film 55 are provided over the substrate 50 (FIG. 9A). Theconnection film 55 is connected to an IC chip or the like.

FIG. 9B is a cross-sectional view of a portion shown by a dashed line ABof the panel, which shows a transistor 412, a light-emitting element413, and a capacitor element 416, each of which is provided in thedisplay region 51, and a pixel group 410 provided in the source driver54.

A sealant 408 is provided in the periphery of the display region 51, thegate drivers 52 and 53, and the source driver 54. The light-emittingelement 413 is sealed by the sealant 408 and an opposite substrate 406.This sealing process is performed to protect the light-emitting element413 from moisture. Although a sealing method using a cover material(such as glass, ceramics, plastic, or metal) is used here, a sealingmethod using a heat curable resin or an ultraviolet curable resin and asealing method using a thin film of metal oxide, metal nitride, or thelike having high barrier capability may also be used. It is preferablethat an element formed over the substrate 50 be formed using acrystalline semiconductor (poly-silicon) having more preferablecharacteristics such as mobility than an amorphous semiconductor.Accordingly, monolithic integration over the same surface can beachieved. As for the panel having the above structure, the number ofexternal ICs to be connected is decreased; therefore, downsizing, weightsaving, and thinner shape can be realized. It is to be noted that, inthis embodiment mode, a reflective polarizing plate 14, a quarter waveplate 15, and a polarizing plate 16 are sequentially stacked over asurface of the substrate 50, which is opposite to the surface over whichthe light-emitting element 413 is formed.

It is to be noted that the display region 51 is formed by a transistorhaving an amorphous semiconductor (amorphous silicon) formed over aninsulating surface as a channel portion, and a circuit for controllingthe display region 51 may be formed by an IC chip. An amorphoussemiconductor can be easily formed over a large-sized substrate by usinga CVD method, and does not need a crystallization process; thus, aninexpensive panel can be provided. In addition, if a conductive layer isformed by a droplet discharging method typified by an ink jetting methodat this time, a more inexpensive panel can be provided. Moreover, the ICchip may be attached to the substrate 50 or the connection film 55 whichis connected to the substrate 50 by a COG (chip on glass) method.

FIGS. 10A and 10B show a state in which an IC chip is mounted on anelement substrate over which a display region having a plurality ofpixels is formed. In FIG. 10A, a display region 51 and gate drivers 52and 53 are formed over a substrate 50. A source driver formed in an ICchip 58 is mounted on the substrate 50. Specifically, the source driverformed in the IC chip 58 is attached to the substrate 50, and iselectrically connected to the display region 51. In addition, powersupply potential, various signals, and the like are supplied to each ofthe display region 51, the gate drivers 52 and 53, and the source driverformed in the IC chip 58 through a connection film 55.

In FIG. 10B, the display region 51 and the gate drivers 52 and 53 areformed over the substrate 50. A source driver formed in an IC chip 59 isfurther mounted on the connection film 55 which is mounted on thesubstrate 50. Power supply potential, various signals, and the like aresupplied to each of the display region 51, the gate drivers 52 and 53,and the source driver formed in the IC chip 59 through the connectionfilm 55.

A mounting method of the IC chip is not particularly limited, and aknown COG method, wire bonding method, TAB method, or the like can beused. Also, a position where the IC chip is mounted is not limited tothe position shown in FIGS. 10A and 10B as long as electrical connectionis possible. Although an example in which only the source driver isformed in the IC chip is shown in FIGS. 10A and 10B, the gate driver maybe formed in the IC chip. Alternatively, a controller, a CPU, a memory,and the like may be formed in the IC chip to be mounted. In addition,the whole source driver or gate driver may not be formed in the IC chipbut only part of a circuit constituting each driver circuit may beformed in the IC chip.

It is to be noted that, by separately forming an integrated circuit suchas a driver circuit by an IC chip and mounting, yield can be improvedand optimization of a process according to characteristics of eachcircuit can be easily performed, as compared with a case of forming allcircuits over a same substrate as a pixel portion.

Although not shown in FIGS. 10A and 10B, a protective circuit may beprovided over a substrate over which the display region is formed. Adischarge path can be ensured by the protective circuit; therefore,noises made by a signal and power supply voltage, or deterioration ordielectric breakdown of a semiconductor element formed over thesubstrate due to a charge which is charged in an insulating film forsome reason can be prevented. Specifically, in a case of FIG. 10A, aprotective circuit can be connected to the wiring which electricallyconnects the connection film 55 to the display region 51. Moreover, theprotective circuit can be connected to each of the wiring whichelectrically connects the connection film 55 to the IC chip 58 in whichthe source driver is formed, the wiring which electrically connects theconnection film 55 to the gate drivers 52 and 53, the wiring (a sourceline) which electrically connects the IC chip 58 in which the sourcedriver is formed to the display region 51, and the wiring (a gate line)which electrically connects the gate drivers 52 and 53 to the displayregion 51.

In the display device of this embodiment mode, reflection of an outsideimage when external light is reflected on the reflective polarizingplate 14 can be suppressed, and display characteristics of an image canbe improved. In addition, light emitted in the light-emitting layer 413can be extracted efficiently, and improvement in brightness of a displayimage can be attempted.

Embodiment Mode 7

In this embodiment mode, examples of electronic apparatuses includingthe display device shown in Embodiment Modes 1 to 6 will be explainedwith reference to FIGS. 11A to 11E.

A television shown in FIG. 11A includes a main body 8001, a displayportion 8002, and the like. The display portion 8002 has a displaydevice including a reflective polarizing plate, a quarter wave plate,and a polarizing plate. By providing the display portion 8002 having thedisplay device, a television in which reflection of an outside image issuppressed and display characteristics of an image are improved can beprovided. In addition, a television in which light emitted in alight-emitting layer can be extracted efficiently and brightness of adisplay image is improved can be provided.

An information terminal device shown in FIG. 11B includes a main body8101, a display portion 8102, and the like. The display portion 8102 hasa display device including a reflective polarizing plate, a quarter waveplate, and a polarizing plate. By providing the display portion 8102having the display device, an information terminal device in whichreflection of an outside image is suppressed and display characteristicsof an image are improved can be provided. In addition, an informationterminal device in which light emitted in a light-emitting layer can beextracted efficiently and brightness of a display image is improved canbe provided.

A video camera shown in FIG. 11C includes a main body 8201, a displayportion 8202, and the like. The display portion 8202 has a displaydevice including a reflective polarizing plate, a quarter wave plate,and a polarizing plate. By providing the display portion 8202 having thedisplay device, a video camera in which reflection of an outside imageis suppressed and display characteristics of an image are improved canbe provided. In addition, a video camera in which light emitted in alight-emitting layer can be extracted efficiently and brightness of andisplay image is improved can be provided.

A telephone set shown in FIG. 11D includes a main body 8301, a displayportion 8302, and the like. The display portion 8302 has a displaydevice including a reflective polarizing plate, a quarter wave plate,and a polarizing plate. By providing the display portion 8302 having thedisplay device, a telephone set in which reflection of an outside imageis suppressed and display characteristics of an image are improved canbe provided. In addition, a telephone set in which light emitted in alight-emitting layer can be extracted efficiently and brightness of adisplay image is improved can be provided.

A portable television shown in FIG. 11E includes a main body 8401, adisplay portion 8402, and the like. The display portion 8402 has adisplay device including a reflective polarizing plate, a quarter waveplate, and a polarizing plate. By providing the display portion 8402having the display device, a portable television in which reflection ofan outside image is suppressed and display characteristics of an imageare improved can be provided. In addition, a portable television inwhich light emitted in a light-emitting layer can be extractedefficiently and brightness of a display image is improved can beprovided. Moreover, the display device of the present invention can beapplied to various televisions such as a small-sized one incorporated ina portable terminal such as a portable phone, a medium-sized one whichis portable, and a large-sized one (e.g., 40 inches or more in size).

It is to be noted that electronic apparatuses according to the presentinvention are not limited to those shown in FIGS. 11A to 11E. Anelectronic apparatus which has a display device including a reflectivepolarizing plate, a quarter wave plate, and a polarizing plate for adisplay portion is included.

As described above, by providing a display portion or the like having adisplay device including a reflective polarizing plate, a quarter waveplate, and a polarizing plate, an electronic apparatus in whichreflection of an outside image is suppressed and display characteristicsof an image are improved can be provided. In addition, an electronicapparatus in which light emitted in a light-emitting layer can beextracted efficiently and brightness of a display image is improved canbe provided.

This application is based on Japanese Patent Application serial No.2005-303770 filed in Japan Patent Office on Oct. 18, 2005, the entirecontents of which are hereby incorporated by reference.

1. An electronic apparatus comprising: a light-emitting layer providedover a first electrode; a second electrode provided over thelight-emitting layer, a substrate provided over the second electrode; ascattering layer provided over the substrate; a reflective polarizingplate provided over the scattering layer; a quarter wave plate providedover the reflective polarizing plate; and a polarizing plate providedover the quarter wave plate, wherein particles each having a differentsize are dispersed in the scattering layer.
 2. An electronic apparatuscomprising: a quarter wave plate provided over a polarizing plate; areflective polarizing plate provided over the quarter wave plate; ascattering layer provided over the reflective polarizing plate; asubstrate provided over the scattering layer; a thin film transistorcomprising a semiconductor film including a source region or a drainregion, which is provided over the substrate; an interlayer insulatingfilm including a contact hole reaching the source region or the drainregion, which is provided over the thin film transistor; a wiringelectrically connected to the source region or the drain region, whichis provided over the interlayer insulating film; a first electrodeprovided over the interlayer insulating film and the wiring; alight-emitting layer provided over the first electrode; and a secondelectrode provided over the light-emitting layer, wherein particles eachhaving a different size are dispersed in the scattering layer.
 3. Theelectronic apparatus according to any one of claims 1 and 2, wherein asecond quarter wave plate is formed between the substrate and thereflective polarizing plate.
 4. The electronic apparatus according toany one of claims 1 and 2, wherein the quarter wave plate is a broadbandquarter wave plate having an effect as a quarter wave plate in a rangeof visible light.
 5. The electronic apparatus according to any one ofclaims 1 and 2, wherein the electronic apparatus is one selected fromthe group consisting of a television, an information terminal device, acamera, and a telephone set.
 6. An electronic apparatus comprising: alight-emitting layer provided over a first electrode; a second electrodeprovided over the light-emitting layer, a substrate provided over thesecond electrode; a scattering layer provided over the substrate; areflective polarizing plate provided over the transparent substratescattering layer; a quarter wave plate provided over the reflectivepolarizing plate; and a polarizing plate provided over the quarter waveplate, wherein particles each having a different refractive index aredispersed in the scattering layer.
 7. An electronic apparatuscomprising: a quarter wave plate provided over a polarizing plate; areflective polarizing plate provided over the quarter wave plate; ascattering layer provided over the reflective polarizing plate; asubstrate provided over the reflective polarizing plate scatteringlayer; a thin film transistor comprising a semiconductor film includinga source region or a drain region, which is provided over the substrate;an interlayer insulating film including a contact hole reaching thesource region or the drain region, which is provided over the thin filmtransistor; a wiring electrically connected to the source region or thedrain region, which is provided over the interlayer insulating film; afirst electrode provided over the interlayer insulating film and thewiring; a light-emitting layer provided over the first electrode; and asecond electrode provided over the light-emitting layer, whereinparticles each having a different refractive index are dispersed in thescattering layer.
 8. The electronic apparatus according to any one ofclaims 6 and 7, wherein a second quarter wave plate is formed betweenthe substrate and the reflective polarizing plate.
 9. The electronicapparatus according to any one of claims 6 and 7, wherein the quarterwave plate is a broadband quarter wave plate having an effect as aquarter wave plate in a range of visible light.
 10. The electronicapparatus according to any one of claims 6 and 7, wherein the electronicapparatus is one selected from the group consisting of a television, aninformation terminal device, a camera, and a telephone set.
 11. Theelectronic apparatus according to any one of claims 1, 2, 6 and 7,wherein the substrate is a transparent substrate.
 12. The electronicapparatus according to any one of claims 1 and 6, wherein the firstelectrode is a reflective electrode, and the second electrode is atransparent electrode.
 13. The electronic apparatus according to any oneof claims 2 and 7, wherein the first electrode is a transparentelectrode, and the second electrode is a reflective electrode.